We intend to define experimental conditions which permit optimal metabolic activity of virulent Treponema pallidum in vitro by monitoring carbohydrate utilization and protein and RNA synthesis. We plan to examine species of proteins and RNA synthesized by treponemes under a variety of conditions by employing high resolution acrylamide gel electrophoresis and radioautography. Attachment of virulent treponemes to eucaryotic cells will be further examined so that treponemal factors required for the host-parasite interaction can be isolated and defined. In addition serum components generated during infection in rabbits which modulate the mitogenic response of lymphocytes will be investigated to determine whether they are of host or treponemal origin and to clarify the specific mechanisms by which these components influence lymphocyte function.